Comment 17 for bug 1583088

If you can reproduce this relative easily, could you try setting QML_USE_GLYPHCACHE_WORKAROUND=1 for unity8. This should do the trick:

stop unity8 && start unity8 QML_USE_GLYPHCACHE_WORKAROUND=1

Can also try these:
QSG_DISTANCEFIELD_ANTIALIASING=subpixel-lowq or gray

Need to determine if that text is being drawn by the DistanceField approach, or using the "native" rendering technique
http://doc.qt.io/qt-5/qml-qtquick-text.html#renderType-prop

If distance field, perhaps the contents of the distance field texture is corrupted somehow. Grabbing the contents of the texture to visually verify it is corrupt or not would be my next step. apitrace might be able to grab the texture. Else would need to write code..